The FBI is investigating the origin of the letter and is not calling it a suicide note

The San Francisco man arrested after what the FBI says are bomb-making materials were found in his home was charged Tuesday with possession of an illegal destructive device.

Ryan Kelly Chamberlain II was unemotional during the 15-minute hearing in U.S. District Court in San Francisco. Judge Nathaniel Cousins ordered a status conference in the case for Wednesday and a detention hearing Thursday.

Chamberlain, 42, was arrested Monday night at Crissy Field, a scenic waterfront area popular with tourists where Golden Gate Bridge spans the Pacific entrance to San Francisco Bay.

Authorities had been looking for him after searching his neighborhood Saturday on a tip that he had "items of great concern" at his home, FBI Special Agent in Charge David Johnson told reporters.

According to an affidavit filed Sunday by agents seeking an arrest warrant, bomb technicians found a glass jar with batteries and a powdery, green substance inside; a model rocket motor; ball bearings and screws; an igniter for home-made bombs; a conductive wire; and a circuit board that could act as a remote-controlled receiver.

The green powder was explosive material, says the affidavit, signed by Special Agent Michael P. Eldridge.

The circuit board would have allowed someone to set off the device "for afar," the filing says without elaborating on how far away someone could have been and detonated a bomb.

There is no mention of ricin being found, contradicting some media reports.

The affidavit says Chamberlain fled from agents after Eldridge interviewed him for a short time at a coffee shop near his apartment on Saturday. After Chamberlain asked to leave, he got in his car and raced away, the agent explained, saying the FBI decided not to pursue out of concern for the safety for people who lived nearby.

The block was closed for some 15 hours over the weekend as investigators searched and cleared the area, CNN affiliate KTVU reported.

If convicted of the illegal destructive device possession charge, Chamberlain faces up to 10 years in prison and a $10,000 fine.

Johnson declined to say what, if anything, Chamberlain had planned to do or what motivated him.

San Francisco Police Chief Greg Suhr said without elaborating that it was clear Chamberlain was "absolutely growing more desperate."

"This subject, Mr. Chamberlain, was a very dangerous and desperate person," Suhr said.

According to CNN affiliate KPIX, Chamberlain had posted an apparent suicide note to friends on Facebook titled "Goodbye." The letter describes a history of depression, despair over a broken relationship and career problems.

"In the span of a few months, everything that mattered to me betrayed me," the writer said.

FBI spokesman Peter Lee said investigators were trying to verify the origin of the post.

Howard Epstein, a former chairman of the San Francisco Republican Party, told KTVU that Chamberlain worked with the local GOP before switching to work on the Democratic side.

"The only one I know that he worked with after he left the party was Gavin Newsom," Epstein told KTVU. "He was an organizer when Gavin ran for mayor." Newsom, a Democrat, is now California's lieutenant governor.

In the letter, the writer says he's had some positive moments in the past few months.

"But so much was broken from this past year-and-a-half, and from moments way back before that, I guess it was insurmountable, and the time's up," the writer says. "Thank you. I'm sorry. I love you."